The invention relates to an apparatus for the gasification of bituminous coal, especially fine coal, comprising a generator which has a container to receive the coal to be gasified, and a feed device which supplies the coal to the container, while keeping the generator closed off so as to maintain the pressure in the generator.
The gasification of bituminous coal under pressure is known per se. Generally it is carried out in so-called generators of which various types of construction are known. In principle, however, all generators feature a container in which the exothermic reactions of the coal to be gasified take place. The slag and ash are drawn off at the lower end of the container while coal is fed to the container at its upper end. Various forms of feed device including gas tight closing-off of the generator are known, as well as a distributor arranged below the feed device to ensure an even loading of the container.
Designs of these so-called fixed bed generators are especially known in which the coal is fed to the container by way of a sluice. The sluice has upper and lower gas tight closures which can be operated either hydraulically or pneumatically.
When the upper closure is open the sluice is not pressurised and the coal to be gasified is fed into the sluice from a supply hopper situated above it. After filling, the upper closure is closed and the sluice is put under pressure from pressurised gas. Only after the sluice has been put under pressure is the lower closure opened so that the coal to be gasified finds its way into the container. The lower closure is then reclosed and the empty sluice is depressurised. The gas released is collected in a gas container which is, in turn, sealed off. The gas so collected can be mixed with the gas generated.
The sluice performs a non-continuous loading of the coal to be gasified. This results in sluice gas losses. Besides this, feeding of the container becomes technically complicated because of the non-continuity of the loading.
In general finely divided coal is gasified, being a mixture of material prepared from general mine coal with a granular size of from 0-30 mm. Fine coal, however, cannot be fed directly into the container of the generator with this range of granular sizes because grain sizes of 0-2 mm interfere with the draught in the body and lead to a high dust incidence in the gas produced. For this reason the fine coal is graded so that material of a granular size of 2-30 mm is fed to the container. In practice, however, according to the quality of the grading and the amount of granular breakdown involved by it, a more or less large proportion of undersize material is present in the fed material.
This method of operating has the disadvantage that it excludes in practice the predominant amount of general mine coal from pressure gasification because investigations have shown that about 70% of general mine coal after preparation comes in granular size of under 2 mm. Furthermore, the grading of such large amounts of coal occasions a considerable expense which can considerably prejudice the economics of pressure gasification.
Of course various processes for the aggregation of fine coal are known.
The conventional process for making briquettes does not have a place in the present invention, on the one hand because it pre-supposes a coal which is dried and which has a maximum grain size of 8-10 mm. Also, conventional briquette processes working with binders, such as bituminous pitch, and also processes working without binders, i.e. hot briquetting processes, require a cooling step following the moulding step, since only then is the required firmness of the briquette produced. The briquette forming process is also expensive.
Pelletising, which is also known, represents a considerable expense also. The agglomerates produced, which begin with nucleus grains occurring in the fed coal and which are built up by the continuous adhesion of fine grains, are known as green pellets. They posses a very low firmness. For this reason the green pellets have to undergo further treatment to render them firmer.